Package javax.management.relation

Provides the definition of the Relation Service. The
Relation Service is used to record relationships between
MBeans in an MBean Server. The Relation Service is itself an
MBean. More than one instance of a RelationService
MBean can be registered in an MBean Server.

A relation type defines a relationship between MBeans.
It contains roles that the MBeans play in the
relationship. Usually there are at least two roles in a
relation type.

A relation is a named instance of a relation type,
where specific MBeans appear in the roles, represented by
their ObjectNames.

For example, suppose there are Module MBeans,
representing modules within an application. A
DependsOn relation type could express the
relationship that some modules depend on others, which could
be used to determine the order in which the modules are
started or stopped. The DependsOn relation type
would have two roles, dependent and
dependedOn.

Every role is typed, meaning that an MBean that
appears in that role must be an instance of the role's type.
In the DependsOn example, both roles would be of
type Module.

Every role has a cardinality, which provides lower
and upper bounds on the number of MBeans that can appear in
that role in a given relation instance. Usually, the lower
and upper bounds are both 1, with exactly one MBean appearing
in the role. The cardinality only limits the number of MBeans
in the role per relation instance. The same MBean can appear
in the same role in any number of instances of a relation
type. In the DependsOn example, a given module
can depend on many other modules, and be depended on by many
others, but any given relation instance links exactly one
dependent module with exactly one
dependedOn module.

A relation instance can be created explicitly, as an object
implementing the Relation interface, typically a RelationSupport.
(A RelationSupport is itself a valid MBean, so it
can be registered in the MBean Server, though this is not
required.) Alternatively, a relation instance can be created
implicitly using the Relation Service's createRelation method.